Telephonic device.



H. E. SHREEVE.

TELEPHONIG DEVICE.

APPLICATION FILED FEB. 17. 1914.

1,159,603. Patented Nov. 9, 1915.

W/fnesses: MVemor: Hekfier/ E. 5hkeeve. 7M g by UNITED STATES PATENT OFFICE.

HERBERT EDWARD SHREEVE, OI MILIBUBN, NEW J'EBSEY, ASSIGNOB '10 WESTERN ELECTRIC COMPANY, OF NEW YORK, N. Y., A CORPORATION OF ILLINOIS.

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Patented Nov. 9, 1915.

. Application filed February 17, 1914. Serial No. 819,256.

To all whom it may concern:

Be it lmown that I, HERBERT EDWARD SHREEVE, a subject of the King of Great Britain, residing at Milburn, in the county of Essex and State of New Jersey, have mvented a certain new and useful Improvement in Telephonic Devices, of which the following is a full, clear, concise, and exact description.

This invention relates to telephonlc devices and more particularly to microphonic devices in which the intimacy of contact of the material composing the resistance varyin medium varies.

The object of this invention isto provide means for automatically regulating or controlling the intimacy of contact of the material of the resistance varying medium of suchdevice to obtain the most beneficial results. r

In accordance with this invention, a differentially wound electromagnet is provided in operative relation to the m1crophonic device. Means are provided whereby an increase or decrease of resistance of the resistance varying mediumcontrols the flow of current through the diflerential windings ofthe electromagnet, causing said electromagnet to react upon the miorophonic device to control the contact relation of the resistance varying medium.

For a more complete understanding of this invention, reference may be had to the accompanying drawings, wherein Figure l is a skeleton view of a transmitter embodying this invention, and Fig. 2 is a skeleton view of a repeater embodying this invention.

As shown in Fig. 1, the transmitter may be of the usual granular carbon type having a granular carbon transmitter button composed of an externally threaded cylindrical member 10, across the open ends of which are flexible members 11 and 12 held in place by means of internally threaded clamping rings 13 and 14 which engage said threaded member 10. The member 11 forms the back electrode of the transmitter. Granular carbon 9 forming the resistance varying me dium is contained within the chamber just described. To the member 12 is secured a front electrode 15 having an outwardly extending stem 16, the end of whiich is in contact with a diaphragm 17. The stem 16 is provided with a shoulder 18 against which rests one end of a spring 19, which insures proper contact being maintained between said stem 16 and said diaphragm 17. 20 represents the usual transmitter mouthpiece. The foregoing description applies to one formof an ordinary carbon 'button transmitter which, for convenience, has been used in connection with the illustrating of one form of this invention. The invention herein embodied will now be described in detail.

To the member 11 is secured a pole piece 30 which coiiperates with a core 31 of an electromagnet. The pole piece 30 and the core 31 are provided with windings 32 and 33. These windings areopposed, 32 being in shunt with the resistance, varying medium 9 of the transmitter, and the windings 33 being in series therewith. One terminal of the winding 33 is connected to the back electrode 11 and the other leads through an impedance coil 34 to one side of battery 35. The other side of battery 35 may 'be connected to the diaphragm 17 through an induction coil primary 36, secondary winding 37 of which is connected with a telephone line. One terminal of the winding 32 is connectedto the back electrode 11' and the other may be connected through an impedance coil 38 to the diaphragm 17. The impedance coils 34 and 38 are in series with the windings 33 and 32 respectively, in order to prevent the passage of alternating currents through said windings. A path for alternating currents is provided through a condenser 39, which shunts the windings 32 and 33 coils 34 and 38.

In microphonic elements, it has been de termined that the resistance of the resistance varying medium variesbetween very wide limits. When the resistance is at the lower limit, the medium is said to be in a packed condition, whereas when at the upper limit, it is said to be in an over sensitive condition. Now, it has furthermore been determined that the efliciency of a microphonic element is greatly increased if the fluctuations of the resistance of the resistance varying medium be confined to closer limits. By the use of this invention, this result is accomplished with the accompanying increased efficiency of the element.

and the impedance With current flowing through the microing medium depending upon the condition of said medium. Assuming that an increase in resistance results, there is immediately an increased How of current through the shunt winding 32 and a decreased flow through the medium 9 and the series winding which, due to said windings being opposed, react upon the member 11 to move- Decreasing the pressure on said medium causes an increase of the resistance'thereof. It will be seen, therefore, that when there is a tendency for the resistance of the resistance varying medium 9 to either increase or decrease, there is an immediate reapportionment of current through the shunt and series'windings 32 and 33, causing a reac- 3 tion upon the member 11. In this way the resistance of the resistance varying medium 9 is controlled by regulating or controlling the intimacy of contact of the material of which said medium is composed.

Referring to Fig. 2 which illustrates a repeater embodying this invention,.50 represents resistance varying medium, and 51 and 52, respectively, represent front and back electrodes of a microphonic or transmitting element of the repeater. Secured to the electrode 52 is a pole piece 53-which cooperates with a core 54 of the receiving element of the repeater. A receiving winding 55 of the repeater is wound over the core 5 1 and the pole piece 53, and is in series with an induction coil secondary 56, the primary -57 of which is in the incoming telephone line. The repeater is provided with a local transmitter circuit comprising the front electrode 51, the resistance varying medium 50, the back electrode 52, a condenser 58 and an induction coil primary 59, the secondary 60 of which is in the outgoing telephone line. One terminal of the induction coil 55 primary 59 is also connected to one side of a battery 65, the other side of which is grounded. The core 54 also carries a winding 66, which is in series with the resistance varying medium 50, and a winding 67 in the flow of alternating current through the series winding 66, an impedance coil 68 is placed'in series therewith, and for like purpose an impedance coil 69 is placed in series with the shunt winding 67 In order to initially regulate the flow of current from battery 65, through the resistance varying medium 50, shunt winding 67 and series winding 66, a variable resistance 7 Dis placed in series therewith.

It will be seen that the intimacy of contact of the material of which the resistance varying medium 50 is compowd is controlled in the same 'manner as is that of the resistance varying medium 9 of Fig. 1. It has been determined that the efiiciency of the microphonic element may be still further increased by placing a resistance 71, having a negative temperature coefiicient in series with the shunt'winding of the device. This resistance 71 has such characteristics that upon an increase in current therethrough the resistance is reduced, thereby permitting a greater flow of current and an increased pull on the electrode of the transmitting element. With a decrease of current through this resistance 71, there is an increase of resistance, resulting in a reduction of current through the circuit and a decreased pull on the electrode of the transmitting element. It is obvious that said resistance 71 may be readily included in series with the shuntwinding 32 of Fig. 1.

What is claimed is:

1. In a telephonic device, a microphonic element, an electromagnet in operative rela tion thereto, and a magnetizing circuit for said electromagnet including a winding in series with, and a winding in shunt with said microphonic element.

2. In a telephonic device, a microphonic element, an electromagnet controlling the operation of said element, and difierential magnetizing windings. for said electromagnet and in circuit with said microphonic element.

3. In a telephonic device, a granular microphonic element, and an electromagnet having differential magnetizing windings thereon in circuit with and in operative relation to said element, said windings coiipcrating upon a flow of current therethrough to relieve the pressure on. the granules of said elementupon a tendency thereof to pack. 1 f

4. In a telephonic device, a microphonic element, resistance varying material there- I in, and an electromagnet having differential magnetizing windings thereon in circuit with and in operative relation to said element, said windings coiiperating upon a flow of current therethrough to regulate the contact relation of said resistance varying material. 60 shunt with said medlum. In order to prevent .5. In a telephonic device, a microphonic element having relatively movable electrodes therein, resistance varying material between said electrodes, at source of current, and an electromagnet controlling the movement of one of said electrodes, said electromagnet having differential windings thereon in circuit with said microphonic element and said source of current.

6. In a telephonic device, a microphonic element, an electromagnet in operative relation thereto, a magnetizing circuit for said electromagnet including a winding in series with and a winding in shunt with said microphonic element, and a resistance having a negative temperature coefficient in series operating upon a flow of current therethrough and acting through said element to relieve the pressure on the granules of said element upon a tendency thereof to pack.

8. In a telephonic device, a granular microphonic element, an electromagnet in operative relation thereto, magnetizing windings for said electromagnet in circuit; with said element, one being in series with and another in shunt with said element, and a resistance having a negative temperature coefficient in series with said shunt winding, said series and shunt magnetizing windings and said resistance cooperating upon a flow of current therethrough and acting through said electromagnet to relieve the pressure on the granules of said element upon a tendency thereof to pack.

9. In a telephonic device,-a granular microphonic element, a vibrating electrode for said element, an electromagnet in operative relation thereto, and diflerential magnetizing windings for said electromagnet in circuit with said element, said differential windings cooperatingiupon a fiow of current therethrough and acting upon said electromagnet to cause said electrode to move outward upon a decrease of resistance of said microphonic element. v

10. In a telephonic device, a granular microphonic element, a vibrating electrode for said element, an electromagnet in operative relation thereto, and differential magnetizing windings for said electromagnet in circuit with said element, said differential windings cooperating upon a flow of current therethrough and acting upon said electromagnet to cause said electrode to move inwardly upon an increase of resistance of said microphonic element.

11. In a telephonic device, a granular microphonicelement, an electromagnet in operative relation thereto and having differential magnetizing windings in circuit with said element, said differential magnetizing windings cooperating upon a flow of current therethrough and acting through said electromagnet to maintain a proper contact relation between the granules of said element.

12. In a telephonic device, a-transmitting element, an electromagnet controlling the operation of said element, and diiierential magnetizing windings for said electromagnet and in circuit with said transmitting element.

In witness whereof, I hereunto subscribe my name this 14th day of February, A. D. 1914. v

HERBERT EDWARD SHREEVE.

Witnesses:

NANON E. TUTHETT, MURRAY V. CONATY. 

